Decimal point locator for slide rules



Oct. 24, 1950 c. cHRlsTEN DECIMAL POINT LOCATOR FOR SLIDE RULES Filed May 2, 1946 INVENTOR.

:Patentedl Oct. 24, v195() DECIMAL POINT LOCATOR FOR SLIDE RULES 1CharlesChristen, Hastings on Hudson, N. Y.

.Application May, 1946, Serial No. 666,655

9Claims. (Cl. E235-64.3)

This invention relates to a device forlocating the decimal point in a number representing the multiplicand or quotient resulting from an arithmetical or mathematical calculation.

The principal object oi the present invention is the provision of a simple device in combination with a conventional slide rule whereb'i7 the user following simple precautions may readily locate .the decimal point between digits of an equation in a visual manner.

The nature of the invention and its distinguishing features and advantages will appear when the following specification is read in con-- junction with the .accompanying drawing, in which- Fig. l is a side view of a conventional slide rule with the device of the present invention applied thereto, certain of the scales of the slide rule having been omitted, and the decimal point locator being shown in its first position.

Fig. 2 is a fragmentary Iside view of the slide rule showing the locator its second position.

Fig. 3 is a view similar to Fig. 2, but showing the locator in its third position.

4 is a side View of 4the cursor or indicator per se.

Fig. 5 is a side view of the digit counter bar per se.

Fig. 6 is a sectional view taken {5*6 of Fig. 3.

7 is an enlarged sectional View tanken on the line l-i of'ig. 1.

Fig. 8 is a fragmentary Side view showing a modiiication.

The device of the present invention is combined with a conventional slide rule comprising a stock. I0, slide ll and cursor or indicator l2. The stock i@ and slide ll have the conventional scales which are incompletely shown yet .sufficiently to give a simple example of the use of the device.

In accordance with the invention., the front transparent panel i3 of the indicator i2 has a decimal point in line with the hairline l5. panel i3 also has a multiplication sign iii and division sign Il sideby in spaced relation to each other. The indicator l2 is constructed to provide a guideway ,iS parallelthe tcp of the stock iii. The panel i3 has a slot i9 therein and the back tra; panel 2 and top spacer have a slot t .ein similar to vthe slot i9. Both lslots openy into the guideivay i3. A digit tallyV 'bar 22 is slidable longitudinally in the guideway IS disposed paron the line allel to the top edge or longitudinal axis of the stock IE5. The bar 22 is rectangular lin crosssection to conform to the crossesectional shape of the guidevvay. The bar has a series ofholes23 extending transversely therethrough yto receive a manipulator consisting of a pin V24 having a.

knob 25. The holes23 in line .with thevslotsfl and 2l are spaced equi-distantly a distance equal to the spacing of the signs land ll. .The

length of the slots I9 and 2| approximates Athe distance between a pair of the holes'23 directly adjacent each other. The bar 22 also hasa reference or tally mark 26 in theform of a short'- line. It occurs midway between they centerpair of holes 23, as shown most clearly in Fig.V 5. stock I0 at the top edge hasan extra 4single scale 2l consisting of ciphers or zeros 28 rep-- resenting minus digits, and Xs 29 representingA The zeros indicate numbers with: These` refer-- ence characters 28 and 29 are spaced equi-dis-4 plus digits. values less than l, such as .0012.

tantly with respect to each other and equal the spacing of the holes 23. It is also to be noted the distance between the decimal point it andv the mark 26 is equal to the distance between any two holes 23 directly adjacent each other. c

From the foregoing it will be understood a slide rule in combination with the above de-l scribed device may be used to shift the relation-4 ship between the number of digits in a problem and the location of the decimal point as the in-I dicator l2 is moved through its .usual positions; as is done in iinding the answer to a certainprob-l lem. For example: 12 2 has three plus digits which are represented on 'the scale 2l thus:

hole 23 by virtue of the slots i9 and 2l.

tion sign I6.

problem aforesaid at the start, as shown .in Fig.v l. The indicator l2 is then moved through its' usual positions by grasping and laterally pushing on the knob 25. At the start of this move-- ment, the bar 22 slides to the right one space before the indicator moves. This shifts the markj 26 one space followed by the movement of the indicator I2 and the bar 22 in unison, as indicated in Fig. 2. Now remembering simply that the problem involves three plus digits, the .indicator I2 is brought intothe required relation to the scale 2l .in which the digit tall;7 rn'arlg` 2.62

The

3 spaces off three digit signs 29 counting the farthest to the left sign 29 and proceeding to the right. This brings the decimal point I4 after the second digit sign 29 thus: 0 X XX which indicates that the answer is twenty-four. If for example it is desired to solve the problem 12 2 3 4 as a continuation of the problem 12 2, it is observed that the mark 26 has shifted one space to the right and that the hairline is in line with the graduation (24) on the scale 2`|, as shown in Fig. 2. The procedure then is as follows: Place the left index of the slide in line with the graduation for 24 and without disturbing the position of the bar 22 or the hairline |5 remove the pin 24 from its present location and place it in the hole which is in registry with the multiplication sign I6. The indicator I2 is again moved through its usual positions by grasping and laterally pushing on the knob 25. At the start of this movement, the bar 22, along with the mark 26, again slides one space to the right and when the hairline I5 arrives at the third factor (3) the mark 26 has shifted two spaces to the right of the point where it started from, which was in line with the decimal point. The hairline I5 is now in line with the graduation for '|2. The right index of the slide is now brought in line with the graduation for 'I2 and, las before, the pin 24 is removed and placed into registry with the multiplication sign I6. The indicator I2 is now moved to the fourth factor (Il) by grasping and laterally pushing on the knob 25. Please note that this movement is the opposite of the other movements and since the multiplication sign and the pin 24 are on the left side of the slot, this movement to the left will not cause any further shifting of the bar 22 or the mark 26. Now remembering that the problem involves ve plus digits, the indicator I2 is brought into the required relation to the scale 21 in which the mark 26 spaces off ve digit signs 29 counting the farthest to the left sign 29 and proceeding to the right. This brings the decimal point I4 after the third digit sign 29 thus: 0 0 XXXX which indicates in a visual manner that the answer is 288.00.

In solving a problem in division, namely,

the procedure for l2 2 as above described is carried out. In such case the hairline I5 will have been brought in line with the graduation (24) and the pin 24 is brought into registry with the division sign II. Since the next operation is one of division, there is no need for resetting the pin. The graduation for 5 on the slide is brought in line with the graduation for 24 and the hairline I5 is brought to the right index by grasping the handle 25. The hairline I5 is in line with the answer, but the graduations shown that it could be .48, 4.8, 48, 480 etc. The digit count for this example is +3 for the numerator and -1 for the deonominator. This gives a sum of +2. When the mark 26 is used to space off +2 digits on the scale 2l, the decima-l point appears thus: 0 0 0 XX XX which denotes the answer to be 4.8.

It will be appreciated that by providing the extra scale 21 it is possible to properly locate the decimal point visually wherein the user is enabled to count off the digits consecutively in a simple manner. This means that the decimal point in even the most dicult problem can be located without making calculations on paper.

By providing a slot, such as the slot I9 in relation to the X and signs, it is possible to use the pin 24 below one or the other of these signs according to a given problem without remembering complicated rules necessary in the use of an ordinary slide rule.

It is to be understood that in lieu of holes 23 extending through the bar, depressions may be used in which case only one slot is required. By providing the holes 23 and the slots 2| at the back the device is useful with the scales on the back of the rule.

Also as shown in Fig. 8 in lieu of the holes 23, the bar 22 may have teeth 30 which coact with a notched rotor 3| carried by the indicator I2 to slide the bar one space to the left or right according to whether the problem is one of multiplication or division. The rotor 3| has arrows 32 and 33, respectively, to indicate the multiplication or division setting of the bar 22. In other respects the device is similar to that shown in Figs. 1 to 7 and similar reference numerals are applied to corresponding features. The rotor 3| functions as a detent in coaction with any two of the teeth 30 because it allows the bar 22 to move one space and then prevents further movement with respect to the indicator I2. The detent 3| is turned to the right for a problem in multiplication. The arrow 32 will point to the proper sign I6. Then by pushing on the left end of the bar 22, the bar will slide one space and be stopped with respect to the indicator |3. On reference to Fig. 8 it will be apparent that as the bar 22 is slid to the right, the tooth 3|] in line with the mark 26 will cam the detent 3| so as to turn it to the left causing the third tooth 3U to the left of the mark 26 to encounter the detent 3|, and so prevent further movement of the bar 22 to the right. In solving the problem 12 2 3 4 with the modification shown in Fig. 8, the procedure heretofore set forth in connection with the pin 24, is followed, the detent 3| is set in the position shown in Fig. 8 for multiplication. The detent 3| is always reset to the multiplication sign after each one space shift of the bar 22 to the right.

For a problem in division the detent 3| is turned to the left bringing the arrow 33 in the proper indicating position with respect to the sign I1. This enables the bar 22 to slide one space to the left by pushing on the right end of the bar. In this event the detent 3| will have turned to the right. The detent is reset, as the case may be, and according to the problem to be solved. After the answer to the problem has been found, the indicator I3 together with the bar 22 in its adjusted position are slid along the stock into juxtaposition to the scale 28 to locate the decimal point according to the number of digits in the answer.

I claim:

1. The combination with a slide rule having a slidable indicator with a hairline and a decimal point on one face thereof, of a minus and plus digit scale on said rule, and a decimal point locator including a digit tally bar with an indicator mark thereon longitudinally adjustable on said indicator, said bar being adjusted with respect to said indicator to displace said mark relative to the decimal point, and said indicator with said bar in the adjusted position being movable as a unit along the rule into position adjacent said scale, thereby showing the decimal point Value of a result on the scale.

2, The combination as set forth in claim 1,

wherein said bar is longitudinally adjustable on said indicator by sliding said bar with respect to the indicator. w

3. The combination as set forth in claim i, wherein said indicator has a slot therein, and said bar has a series of equi-distantly spaced holes therein in line with said slot, and a pin engageable in any one of said holes through said slot, for causing adjustment of the bar with respect to the indicator and the movement of the bar and indicator in unison for the stated purpose.

4. The combination with a slide rule having a stock and an indicator having a hairline slidable along the stock, of a digit tally bar slidable 1ongitudinally with and with respect to said indicator, said indicator having and -zsigns thereon, side by side in spaced relation and a decimal point in line with the hairline, said bar having a digit tally mark thereon which is displaced relative to the decimal point upon adjustment of said bar with respect to the indicator, and a minus and plus scale on said stock, said indicator with the bar in the adjusted position being movable in unison along said stock, thereby showing the decimal point value of a result on said scale.

5. The combination as set forth in claim 4, wherein said indicator has a slot therein adjacent said and -zsigns, said bar has a series of holes therein spaced equi-distantly, and a manipulator insertable in any one of said holes While extending through said. slot to move the bar and indicator as stated.

6. The combination with a slide rule having a slidable indicator having a hairline and a deciu mal point in alignment with each other and multiplication and division signs spaced apart, of a digit tally bar slidable longitudinally with and with respect to said indicator, said bar having a digit tally mark thereon for alignment with said hairline, said bar having a series of teeth, a notched rotor on said indicator which coacts with said teeth to adjust the bar to the right or left to displace said mark relative to the decimal point, and to cause said indicator and bar in adjusted position to move in unison upon the manipulation of said bar, said rotor having arrows or the like thereon which point to said signs respectively to indicate the multiplication or division setting of the bar, and a minus and plus digit scale on the stock, said indicator and bar being movable in unison along said rule into position adjacent said scale showing the decimal point value of a result on said scale.

7. The combination with a slide rule having a slidable indicator with a hairline and a decimal Apoint thereon, of a minus and plus digit scale on said rule along one longitudinal edge thereof, said indicator having a guideway therein paralleling said edge, a digit tally bar having a digit tally mark thereon slidably adjustable in said guideway with respect to the indicator to displace said mark relative to the decimal point, and means to engage said bar and said indicator to cause the movement of said bar together with the indicator along the rule into juxtaposition to said scale to show the decimal point value of a result on said scale.

8. The combination as set forth in claim 7, wherein said last means consists of a manipulator adapted to extend through aligned slots in said indicator and any one of a series of holes in said bar.

9. The combination with a slide rule having a stock and an indicator having a hairline slidable along the stock, of a digit tally bar adjustable with respect to said indicator and also movable therewith along said stock, said indicator having and signs thereon side by side in spaced relation and a decimal point in line with said hairline, said bar having a digit tally mark between said signs for alignment with said hairline, -said indicator having a slot therein and said bar having a series of holes therein spaced according to the spacing of said signs whereby a suitable manipulator may be engaged with said bar to adjust the bar with respect to the indicator and to move bar and indicator in unison, along said stock, and a minus and plus digit scale on said stock, said bar when adjusted with respect to the indicator displacing saidrrnark relative to the decimal point, and said indicator and the bar when moved in unison along. said stock into juxtaposition to said scale showing the decimal point value of a result on said scale.

CHARLES CHRISTEN.

Country Date Great Britain July 28, 1938 Number 

